This is the 17562nd most frequent Korean word.
세계관세기구
World Customs Organization (WCO).
Here, "세계관세기구" is used as the subject of the sentence referring to the organization itself.
세계관세기구는 국제 무역 규제에 중요한 역할을 합니다.
The World Customs Organization plays an important role in regulating international trade.
In this sentence, "세계관세기구" is part of a prepositional phrase indicating the organization to which member states belong.
많은 나라들이 세계관세기구의 회원국입니다.
Many countries are member states of the World Customs Organization.
The term "세계관세기구" here helps specify the regulations issued by this organization.